1. Field of the Invention
The present invention is directed to systems for controlling the distribution of items, such as digital content. In particular, the present invention is directed to such systems that support multiple trust zones.
2. Description of Related Art
One of the most important issues impeding the widespread distribution of digital works (i.e. documents or other content in forms readable by computers), via electronic means, and the Internet in particular, is the current lack of ability to enforce the intellectual property rights of content owners during the distribution and use of digital works. Efforts to resolve this problem have been termed “Intellectual Property Rights Management” (“IPRM”), “Digital Property Rights Management” (“DPRM”), “Intellectual Property Management” (“IPM”), “Rights Management” (“RM”), and “Electronic Copyright Management” (“ECM”), collectively referred to as “Digital Rights Management (DRM)” herein. There are a number of issues to be considered in effecting a DRM System. For example, authentication, authorization, accounting, payment and financial clearing, rights specification, rights verification, rights enforcement, and document protection issues should be addressed. U.S. Pat. Nos. 5,530,235, 5,634,012, 5,715,403, 5,638,443, and 5,629,980, the disclosures of which are incorporated herein by reference, disclose DRM Systems addressing these issues.
In the world of printed documents and other physical content, a work created by an author is usually provided to a publisher, which formats and prints numerous copies of the work. The copies are then sent by a distributor to bookstores or other retail outlets, from which the copies are purchased by end users. While the low quality of copying and the high cost of distributing printed material have served as deterrents to unauthorized copying of most printed documents, it is far too easy to copy, modify, and redistribute unprotected digital works with high quality. Accordingly, mechanisms of protecting digital works are necessary to retain rights of the owner of the work.
Unfortunately, it has been widely recognized that it is difficult to prevent, or even deter, people from making unauthorized copies of electronic works within current general-purpose computing and communications systems such as personal computers, workstations, and other devices connected over communications networks, such as local area networks (LANs), intranets, and the Internet. Many attempts to provide hardware-based solutions to prevent unauthorized copying have proven to be unsuccessful. The proliferation of high band-width “broadband” communications technologies and the development of what is presently known as the “National Information Infrastructure” (NII) will render it even more convenient to distribute large documents electronically, including video files such as full length motion pictures, and thus will remove any remaining deterrents to unauthorized copying and distribution of digital works. Accordingly, DRM technologies are becoming a high priority.
Two basic DRM schemes have been employed, secure containers and trusted systems. A “secure container” (or simply an encrypted document) offers a way to keep document contents encrypted until a set of authorization conditions are met and some copyright terms are honored (e.g., payment for use). After the various conditions and terms are verified with the document provider, the document is released to the user in clear form. Commercial products such as CRYPTOLOPES™ and DIGIBOXES™ fall into this category. Clearly, the secure container approach provides a solution to protecting the document during delivery over insecure channels, but does not provide any mechanism to prevent legitimate users from obtaining the clear document and then using and redistributing it in violation of content owners' intellectual property.
In the “trusted system” approach, the entire system is responsible for preventing unauthorized use and distribution of the document. Building a trusted system usually entails introducing new hardware such as a secure processor, secure storage and secure rendering devices. This also requires that all software applications that run on trusted systems be certified to be trusted. While building tamper-proof trusted systems is a real challenge to existing technologies, current market trends suggest that open and untrusted systems, such as PC's and workstations using browsers to access the Web, will be the dominant systems used to access digital works. In this sense, existing computing environments such as PC's and workstations equipped with popular operating systems (e.g., Windows™, Linux™, and UNIX) and rendering applications, such as browsers, are not trusted systems and cannot be made trusted without significantly altering their architectures. Of course, alteration of the architecture defeats a primary purpose of the Web, i.e. flexibility and compatibility.
U.S. Pat. No. 5,634,012, the disclosure of which is incorporated herein by reference, discloses a system for controlling the distribution of digital documents. Each rendering device has a repository associated therewith. A predetermined set of usage transaction steps define a protocol used by the repositories for enforcing usage rights associated with a document. Usage rights persist with the document content. The usage rights can permit various manners of use such as, viewing only, use once, distribution, and the like. Usage rights can be contingent on payment or other conditions.
Conventional implementations of DRM Systems work well in a single activation server system, where the activation server provides one or more clients with a public and private key pair, or other identification mechanism, during activation to allow the client to access and use the protected content based on provisions specified by a license issued by one or more license servers. The single activation by a single activation server system allows the same activation to be used to enforce usage rights for all the content protected with the DRM System. By allowing the activated client to discern cryptographic signatures, signatures by license servers that have not been activated by the same activation system will be rejected which means that there will be interoperability problems if more than one activation system is provided in the DRM System. However, the multiplicity of parties to electronic transactions and various business models in use today often results in multiple activation systems and the resulting multiplicity of activations for content from various systems. Such multiple activations complicate the user experience because different sets of keys, or other identification mechanism, are required to use different content.